Method and apparatus for automatically adjusting speaker and microphone gains within a mobile telephone

Abstract

The mobile telephone is provided with the capability for automatically adjusting the gain of a microphone of the telephone based upon the detected noise level in which the cellular telephone is operated. As the noise level increases, the gain of the microphone is automatically decreased, thereby compensating for the natural tendency of telephone users to speak more loudly in noisy environments. Also, by decreasing the microphone gain, any clipping that might otherwise occur as a result of the user speaking more loudly is avoided and the signal-to-noise ratio is not thereby decreased. Furthermore, because the microphone gain decreases, the volume level of the voice of the user as it is output from the other party's telephone is not unduly loud. Hence, the other party need not manually decrease the speaker gain of his or her telephone. In the exemplary embodiment, the cellular telephone includes a digital signal processor configured or programmed to apply the detected noise level to look-up tables relating various noise levels to appropriate speaker and microphone gain levels. Also, in the exemplary embodiment, the mobile telephone includes a speaker and the gain of the speaker is adjusted to increase in response to an increase in the background noise level. A device for adjusting gain in a microphone of a wireless communications device includes adjustable digital gain logic coupled to the microphone and a limiter coupled to the adjustable digital gain logic. The limiter performs peak detection on a speech signal that is input to the microphone.